The Question is from neet-chemistry surface-chemistry , and it was created by the author P SRAVAN KUMAR

Question

Which of the following contributes to the cleansing action of soap BUT NOT detergents?

P SRAVAN KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Differences in the chemical composition and behavior of soaps and detergents in hard water.
 **Related Topics**:  Surface tension, micelle formation, emulsification, hard water, calcium and magnesium ions.
 **Prerequisites**: Basic understanding of soap and detergent structures and their interaction with water and grease.
## SOLUTION PATHWAY
**Given Information**:
The question asks for a cleansing action of soap that is *not* shared by detergents.
**Method & Steps**:
1. **Identify the cleansing actions:** Soaps and detergents both lower surface tension, emulsify grease, and form micelles to trap dirt and grease.
  Reasoning: These are common mechanisms for both types of cleaning agents.
  Formula/Rule: None directly applicable.
2. **Consider the effect of hard water:** Soaps react with hard water ions (calcium and magnesium ions) to form insoluble precipitates (soap scum).
  Working: This precipitation reduces the effectiveness of soap and leaves a residue.
  Key Point: Detergents, being synthetic, generally do not form insoluble precipitates with hard water ions.
3. **Compare the actions:**  The formation of precipitates is a unique characteristic of soaps in hard water. 
  Result: Precipitation with hard water ions is a cleansing action of soap, but not of detergents.
  Verification: Detergents are designed to overcome the limitations of soaps in hard water.
 ## OPTION ANALYSIS
A ✓: Precipitation with hard water ions: This is correct. Soaps form insoluble precipitates with hard water ions (like $Ca^{2+}$ and $Mg^{2+}$), reducing their effectiveness. Detergents, however, generally do not form these precipitates.
B :x: Lowering of surface tension: Both soaps and detergents lower surface tension, aiding in wetting and spreading.
C :x: Emulsification of grease: Both soaps and detergents emulsify grease, breaking it down into smaller droplets that can be easily rinsed away.
D :x: Formation of micelles: Both soaps and detergents form micelles, which encapsulate grease and dirt, allowing them to be removed with water.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing soaps and detergents: Understanding the chemical differences is crucial.
  How to avoid: Focus on the chemical composition and their interaction with hard water.
  2.Overlooking the effect of hard water: Hard water significantly impacts soap's performance. 
  How to avoid: Remember that soap scum formation is a key difference.
 **Quick Tips**:
  1.Remember that soaps are salts of fatty acids, while detergents are synthetic surfactants.
  2.Soap scum is a tell-tale sign of soap reacting with hard water.

P SRAVAN KUMAR · Answer

The correct Option is "Precipitation with hard water ions"

P SRAVAN KUMAR · Answer

Lowering of surface tension

P SRAVAN KUMAR · Answer

Emulsification of grease

P SRAVAN KUMAR · Answer

Formation of micelles

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